Exposure time controls for cameras operating with flash illumination

ABSTRACT

A camera which can provide flash illumination, particularly for reducing the exposure time. The camera shutter is automatically closed when the charge of a timing capacitor increases to a given extent. Simultaneously with the creation of the flash illumination, a suitable circuit generates an electrical signal which is used to charge the capacitor so as to coact therewith for achieving a predetermined exposure time. The capacitor is also charged by a photosensitive element which responds to the light created during flash illumination, so that the predetermined exposure time will be reduced to the extent that the capacitor is charged by the photosensitive element.

[11] 3,748,978 July 31, 1973 United States Patent [191 Yoshimura et al.

3,610,122 10/1971 Biber...............r................... ..95/10 1 1EXPOSURE TIME CONTROLSv FOR CAMERAS OPERATING WITH FLASH ILLUMINATION[75] Inventors: Hirofumi Yoshimura, Okaya;

Primary Examiner-Samuel S. Matthews Assistant Examiner-Michael L.Gellner Attorney-Harold D. Steinberg et al.

ABSTRACT Japan Filed! 1971 A camera which can provide flashillumination, partic- 21 Appl. No.: 195,305

ularly for reducing the exposure time. The camera shutter isautomatically closed when the charge of a .30] timing capacitorincreases to a given extent. Simulta- Fm'eign pp l y Data neously withthe creation of the flash illumination, a Nov. 9, 1970 suitable circuitgenerates an electrical signal which is used to charge the capacitor soas to coact therewith for achieving a predetermined exposure time. Thecapacitor is also charged by a photosensitive element which responds tothe light created during flash illumi' no mm 0 lb /31 5 Q E C "0 m m l"5 u 9 u" .6 r. a .0. "m n V mh UIF 1 211 18 555 11.1.

/10 CE nation, so that the predetermined exposure time will be reducedto the extent that the capacitor is charged by the photosensitiveelement.

[56] References Cited UNITED STATES PATENTS 9 Claims, 4 Drawing FiguresEXPOSURE TIME CONTROLS FOR CAMERAS OPERATING WITH FLASH ILLUMINATIONBACKGROUND OF THE INVENTION The present invention relates to cameras.

The present invention relates in particular to cameras which are capableof automatically determining the exposure time.

Thus, it is conventional to provide cameras capable of controllingautomatically the exposure time with structures which includephotoelectric elements adapted to change their resistance value or aphotoelectric current value in accordance with the light intensity at anobject which is to be photographed. Such cameras are of advantage inthat the exposure time can be controlled electrically in an automaticmanner in accordance with the intensity of the light at the object whichis to be photographed.

However, cameras of this type have a disadvantage in that the quality ofthe photograph may be undesirably influenced by factors such as movementof the object which is photographed or movement of the camera when it ishand-held during relatively long exposure times which may be longer thanan exposure time on the order of one thirtieth second, for example.Under these latter conditions the operator normally may not be awarethat the hand-held camera may move during exposure so as to create apoor photograph, and for this reason it has been proposed to incorporateinto a camera a device which will indicate the latter conditions to theoperator before an exposure is made, so as to achieve in this wayphotographs of better quality. A preferable arrangement for solving thislatter problem is one where the camera includes a structure informingthe operator that the exposure should be made with flash illuminationunder conditions where the exposure time would be too long for a properexposure when the camera is hand-held, so that with the added lightachieved by the flash illumination it is possible to reduce the exposuretime, and thus it is still possible to automatically provide an exposuretime which is short enough to prevent movement of a hand-held camerafrom undesirably influencing the quality of the photograph.

Cameras of the above. general type are usually provided withphotosensitive elements such as a CdS (cadmium sulfide) resistor, whichin a well known manner responds to light so as to control the exposuretime. However, this latter type of photosensitive element is not highlysensitive in its response to light, so that when there is a relativelysmall extent of illumination the CdS type of photosensitive element isincapable of responding with sufficient rapidity to the instantaneousflash of light created with an automatic flash structure. As a resulteven when a photograph is made with additional illumination from a flashstructure there is the danger of an exposure time which is too long ifthe shutter is controlled by a signal determined by the response of aCdS type of photosensitive element to the flash illumination.

In order to solve this latter problem it has been essential to correctthe exposure time determined on the basis of the intensity of the lightreceived by the CdS element, under conditions where the object to bephotographed is illuminated with flash illumination. Such correction hasbeen achieved by way of a fixed resistor connected in parallel with theCdS element through a suitable switch in a suitable electrical circuit.During exposure with flash illumination, the camera operator will closethis latter switch so that the exposure time will be determined by atime constant of an RC timer circuit which includes the latter fixedresistor and a capacitor set to achieve a constant exposure time whichmay, for example, be one thirtieth second. This latter capacitor ischarged on the basis of the sum of the electric current flowing throughthe CdS element and the fixed resistor, so that the shutter is closedafter an exposure time which is substantially less than the exposuretime which would otherwise be determined solely by way of the fixedresistor and capacitor without the additional charge received from theCdS element. Exposure time correcting circuits of this latter type aredisclosed in the Japanese Patent Publication No. 1968-10260 and in 0.8.Pat. No. 3,326,103.

However, these latter types of structures require the operator to selectthe use of the fixed resistor during exposure with flash illumination,and this requirement is a serious disadvantage since the operator mayforget, for example, to connect the fixed resistor to the circuit.

SUMMARY OF THE INVENTION It is accordingly a primary object of thepresent invention to provide a structure which will avoid the abovedrawbacks.

In particular, it is an object of the present invention to provide astructure capable of correcting the timing of the exposure underconditions where the exposure is made with flash illumination while atthe same time avoiding any erroneous operation of the camera due toforgetfulness on the part of the operator.

Thus, it is an object of the invention to provide for a structure of theabove type circuitry which will automatically correct the exposure timein a highly reliable manner in the event that flash illumination is usedunder conditions as set forth above.

Another object of the present invention is to provide a structure of theabove type which will not be capable of undesirably creating flashillumination if the operator forgets to remove the flash structure fromthe camera.

It is also an object of the present invention to provide a structure ofthe above general type which includes a photosensitive means which has agreater degree of sensitivity to light than the conventional CdSelement.

Yet another object of the present invention is to provide a structure ofthe above general type which is relatively simple and inexpensive tomanufacture while at the same time operating very reliably to achievethe desired results.

According to the invention the camera includes a shutter-opening meansfor starting an exposure and a shutter-closing means for terminating theexposure. A timing circuit means is electrically connected with theshutter-closing means for actuating the latter to close the shutter soas to terminate the exposure. This timing circuit means includes acapacitor means which actuates the shutter-closing means when theterminal voltage of the capacitor means rises to a predetermined extent.A photosensitive means also forms part of the timing circuit means andis electrically connected with the capacitor means for charging thelatter in accordance with light which is received by the photosensitivemeans. A flash circuit means is provided for creating flashillumination, when the flash circuit means has a suitable source offlash illumination connected thereto, and the photosensitive meansresponds to the light created during flash illumination for charging thecapacitor means. An signal-generating circuit means is electricallyconnected with the flash circuit means for rendering the latteroperative to create flash illumination in synchronism with opening ofthe shutter and for generating an electrical signal simultaneously withthe creation of the flash illumination. A charging means is electricallyconnected to the signal-generating circuit means to receive theelectrical impulse therefrom and is also electrically connected to thecapacitor means for charging the latter to a predetermined extent inresponse to receiving the electrical signal from the signalgeneratingcircuit means. This charging of the capacitor means by the chargingmeans with the signal from the signal-generating circuit means providesa predetermined exposure time which is diminished to the extent that thecapacitor means is charged by the photosensitive means when the latterreceives the light from the flash illumination.

BRIEF DESCRIPTION OF DRAWINGS The invention is illustrated by way ofexample in the accompanying drawings which form part of this applicationand in which:

FIG. 1 is a schematic block diagram of the present invention;

FIG. 2 is a wiring diagram of one embodiment of the present invention;

FIG. 3 is a wiring diagram of another embodiment of the presentinvention; and

FIG. 4 is a graph illustrating the manner in which the structure of theinvention operates.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the block diagram ofFIG. 1, there is illustrated therein a shutter-closing means 1 which ina well known manner is electrically actuated for closing a shutter so asto terminate the exposure. A timing circuit means 2 is electricallyconnected with the shutterclosing means 1 so as to actuate the latter toclose the shutter after elapse of an exposure time determined by thetiming circuit means 2. This timing circuit means 2 includes a timingcapacitor, referred to in greater detail below, and this capacitor ischarged by a charging means 3 which serves to provide with the capacitora predetermined exposure time. The charging circuit means 3 is renderedoperative when it receives an electrical signal or impulse from a signalor impulsegenerating circuit means 4. This impulse-generating circuitmeans 4 is electrically connected with a flash circuit means 5 to renderthe latter operative in synchronism with opening of the shutter so thatthe flash circuit means 5 will create flash illumination, theimpulse-generating circuit means 4 generating simultaneously with thecreating of the flash illumination an electrical impulse which operatesthe charging means 3 so that it will coact with the timing capacitor ofthe timing circuit means 2 in order to provide a predetermined exposuretime.

With this construction it is to be assumed that the flash circuit means5 is electrically connected to the impulse-generating circuit means 4when the operator inserts a synchro-plug of a flash-gun into asynchrosocket of the camera. With the structure in this condition, anenergy storage part of the flash circuit means 5 is supplied with energyfor generation of electrical pulses from the power source used to createthe flash illumination, and this latter operation is brought about byactuating the flash circuit means 5 in order to create the flashillumination. When a synchronous switch of the impulse-generatingcircuit means 4 is closed simultaneously with opening of the shutter,the electrical pulse is generated by the impulse-generating circuitmeans 4 in synchronism with the creating of the flash illumination bythe flash circuit means 5. This impulse which is generated drives thecharging means 3 so as to charge the capacitor of the timing circuitmeans 2, this charge being determined by the sum of the output currentof the charging circuit means 3 and the charge on the capacitor derivedfrom a photosensitive means of the timing circuit means, thisphotosensitive means responding to light so as to contribute to thecharge of the timing capacitor. When the terminal voltage of the timingcapacitor reaches a predetennined value after elapse of the requiredcharging time, the shutterclosing means 1 is automatically actuated toclose the shutter and terminate the exposure. Under these conditions theexposure time will never be greater than the time determined by thecharging of the timing capacitor with the charging means 3 from theimpulse derived from the impulse-generating circuit means 4, since thecapacitor is also simultaneously charged due to the operation of thephotosensitive means which responds also to the light created by theflash illumination.

Referring to the embodiment of the invention which is illustrated inFIG. 2, it will be seen that the parts which form the timing circuitmeans 2 includes the photosensitive means 6 in the form of a solarbattery and the timing capacitor 7 which is electrically connected withthe solar battery 6, this timing capacitor 7 being bridged by a normallyclosed trigger switch 8.

The charging means 3 of the embodiment of FIG. 2 includes the transistor9 and the electrical resistors 10l2 electrically connected in circuittherewith as illustrated in FIG. 2, this charging circuit means alsoincluding the SCR 13.

The impulse-generating circuit means includes the diode 14, thesynchronous switch 15 which automatically closes when the shutterreaches its fully open position, as is well known, and theimpulse-generating coil 16.

The flash circuit means 5 includes the resistor 17, a suitable socket toconnect the flash bulb 18 into the circuit, a capacitor 19 to generate apulse for firing the flash bulb, and a power source 20.

An electrical connecting means is provided for removably connecting theflash circuit means 5 to the impulse-generating circuit means 4. Thisconnecting means includes the schematically illustrated terminals a, band a, b. The former terminals are electrically connected with thelatter terminals, respectively, when the flash gun is mounted on thecamera.

Thus, when the flash circuit means 5 is electrically connected into thecircuit by way of these terminals, so as to enable the camera to makeexposures with flash illumination, the energy from the power source 20is stored in the capacitor 19 through the resistor 17 and the bulb 18.The camera includes a shutter-opening means formed by the switch 22which is automatically closed when the shutter-tripping plunger of thecamera is depressed, and the closing of this switch 22 connects thepower source 21 into the circuit and energizes the relay 23 which in aknown manner releases the cocked shutter so that it will automaticallyassume its open position and which at the same time opens the normallyclosed switch 8. Thus, during the final range of movement of theshutter-operating plunger the cocked shutter is released so that itautomatically opens and simultaneously the trigger switch 8 is opened.

When the shutter has almost reached its fully open position it will in awell known manner automatically close the synchronous switch so as tooperate the flash circuit means to create flash illuminations insynchronism with exposure of the film by the open shutter. The closingof the switch 15 will cause the charge stored in the capacitor 19 to bemomentarily converted into an electrical pulse which fires the bulb 18and which in addition is applied through the terminals of the electricalconnecting means to the coil 16.

This coil 16 of the impulse-generating circuit means will now bringabout generation across the opposite ends of the coil of a potentialpulse in the form of an electrical impulse which is applied through thediode 14 to the gate of the SCR 13 so as to render the latterconductive. As a result the transistor 9 is also rendered conductive andthe capacitor 7 is charged with the output current of the transistor 9.At the same time the photosensitive means formed by the solar battery 6responds not only to the ambient light but also to the light created bythe firing of the bulb 18 so as to additionally charge the timingcapacitor 7. Thus the light received by the solar battery 6 generates acurrent which also contributes to the charge of the capacitor 7.

When the terminal voltage of the capacitor 7 rises to a given value, theshutter-closing means 1 is automatically actuated to close the shutterand terminate the exposure. Thesmaller the amount of light reflectedfrom the object to be photographed to the photosensitive means 6, thesmaller is the extent to which the capacitor 7 is charged from thephotosensitive means 6 due to photoelectrically converted currentthereof. However, the exposure time never exceeds a time which isdetermined by the output current of the transistor 9 and the capacitor7, this latter time being a time constant which cannot be exceeded sincethis latter exposure time will be diminished to the extent that thecapacitor 7 is charged with the photosensitive means 6 in response tolight received thereby.

Thus, with this embodiment of the invention which is illustrated in FIG.2, the closing of the synchronous switch 15 which is conventional, whenthe flash circuit means is electrically connected with the camera,brings about a correction of the exposure time which otherwise would beachieved only by way of the photosensitive means 6 itself.

It is to be noted that with the embodiment of FIG. 2 when the flash bulb18 is not connected into the circuit of the flash circuit means 5, theexposure time correcting circuitry will not operate since the capacitor19 cannot be charged. The flash bulb 18 must be connected into thecircuit in order to make it possible to charge the capacitor 19. Thus,this embodiment has an advantage in that the exposure time is correctedonly during flash photography while at the same time other types ofphotography, with available natural light, can be properly carried outeven if the operator should carelessly leave the flash circuit means 5connected to the camera.

In the embodiment of the invention which is illustrated in FIG. 3, thetiming circuit means 2 includes the solar battery 24, which forms thephotosensitive means, the normally closed trigger switch 25, and thecapacitor means 26, all of these components operating in the manner ofthe corresponding components of FIG. 2.

The charging means 3 of FIG. 3 is formed by the transistor 27, theresistors 28 and 29, and a monostable multivibrator which includes thetransistors 33 and 34, a capacitor 35, and resistors 30-32.

The impulse-generating circuit means 4 of the embodiment of FIG. 3includes a booster transformer having the coils 37 and 38 as well as adiode 36, a capacitor 39, and the synchronous switch 40 which operatesin the same way as the switch 15 referred to above.

The flash circuit means 5 of the embodiment of FIG. 3 includes thedischarge tube 41, a trigger coil 42, a resistor 43, a capacitor 44 fortriggering the discharge tube 41, and a power source 45. The terminalsa", b" and a, b form an electrical connecting means for removablyconnecting the flash circuit means to the camera in the same way as wasdescribed above in connection with FIG. 2. 7

With the embodiment of FIG. 3 when the electrical connection isestablished through the above terminals of the electrical connectingmeans, and the synchronous switch 40 is in its open position, theelectrical charge from the power source 45 is stored in the capacitor 44through the resistor 43, so that this charge in the capacitor 44 stillis not available for triggering the discharge tube 41. Part of thischarge is also stored in the capacitor 39 through the terminals a" anda".

The camera structure used with the embodiment of FIG. 3 is the same asthat used with the embodiment of of FIG. 2, so that when the shutter hasalmost reached its fully open position the shutter will automaticallyclose the synchronous switch 40 in the manner described above. Now theelectrical charge which has been stored in the capacitor 44 is convertedinto a momentary electrical pulse which is in turn applied to thetrigger coil 42 so as to trigger the discharge tube 41 and thus createthe flash illumination. In synchronism with this latter operation theelectrical charge which was stored in the capacitor 39 also ismomentarily converted into an electrical current which flows through thecircuit which includes the transformer coil 38 and the synchronousswitch 40. An impulse is thus generated across the opposite ends of thecoil 38, and this impulse is amplified by the transformer coil 37. As aresult a positive potential pulse is applied through the diode 36 to thebase of the transistor 33, and this transistor 33 is brought into itsstate of conductivity while the transistor 34 is transferred into itsnon-conductive state. As a result the transistor 27 is renderedconductive, and the capacitor 26 is charged with the output of thetransistor 27. Inasmuch as the state of conductivity of the transistor33 is maintained only for a predeter mined time depending upon theresistance 31 and the capacitor 35, the resistance value of the resistor31 and the capacity of the capacitor 35 are chosen or regulated in sucha way that the time which depends upon the resistor3l and capacitor 35never exceeds the predetermined time essential for flash photography,namely the time required for the terminal voltage of the capacitor 26 torise due to transfer of the transistor 27 to its state of conductivity,assuming that there is no influence from the solar battery. As a resultthe exposure time never exceeds the predetermined time constant, asdetermined by operation without the solar battery, since the latterprovides and additional charge simultaneously with the flashillumination.

The graph of FIG. 4 illustrates the manner in which the capacitors 7 and26 operate in order to achieve the corrections in accordance with thepresent invention. In the graph of FIG. 4, the ordinate represents theterminal voltage of the timing capacitor 7 or 26, while the abscissarepresents time according to increments which represent fractional partsof a second. Thus, the three curves of FIG. 4 illustrate the manner inwhich the terminal voltage rises during the exposure time which isrepresented along the abscissa. The time constant achieved without theuse of the solar batteries 6 or 24 is represented by the curve p. Thiscurve represents the speed with which the terminal voltage of thecapacitor rises without any influence from the photosensitive meansformed by the solar battery 6 of FIG. 2 or the solar battery 24 of FIG.3.

The curve r illustrates how the terminal voltage of the capacitor risesas a result of the influence of the solar battery alone.

As is apparent from the above description, with both embodiments of theinvention the terminal voltage is rising not only as illustrated by thecurve 1 but also simultaneously as illustrated by the curve r, so thatthe actual rise in terminal voltage is represented by the dotted linecurve q, which represents the sum of the curves p and r, and thus it isclear that the terminal voltage of the timing capacitor will reach therequired value for triggering the closing of the shutter in a time whichis shorter than the predetermined time provided by the time constant asillustrated by the curve p.

Thus, in accordance with the present invention it is possible to correctthe exposure time automatically in response to a signal at the instantof flash light emission simply by connecting the impulse generatingcircuit means with the flash circuit means, and in addition it ispossible to carry out available light photography such as photographywith daylight inasmuch as the exposure time correcting circuit is notrendered operative when there is no flash illumination. With previouslyknown constructions, however, the exposure time correcting circuit isindeed activated even when there is no flash illumination, so thatunless the flash structure is removed there will unavoidably be anundesirable influence on the exposure which is made under availablelight conditions or daylight conditions without flash.

Also, in accordance with the invention the instant of flash illuminationis precisely synchronized with the instant when the shutter has beenopened, and the exposure time is determined with a minimum error inaccordance with the light reflected from the object which isphotographed, so as to result in photographs of high quality even whenexposures are made under conditions where otherwise any slight movementof a handheld camera would result in a blurred image or a photograph ofpoor quality.

A further advantage of the invention resides in using for thephotosensitive means a photoelectromo'tive element of highphotosensitivity, such as the solar batteries 6 and 24, since this typeof element responds very quickly to the flash illumination and therebyassures a more precise correction. However, even if the photosensitivemeans were in the form of a CdS element which has a relatively lowphotosensitivity, there would still be achieved with the presentinvention a correction of the exposure time with an error considerablysmaller than would otherwise be achieved.

Although the structure of the present invention has been described aboveand illustrated in the drawing as including the charging circuit means3, the impulse generating circuit means 4, and the flash circuit means5, details of which are illustrated in FIGS. 2 and 3, these circuits maybe replaced by equivalents which cooperate together to achieve also theresults of the present invention.

What is claimed is:

1. In a camera, shutter-opening means for opening a shutter to start anexposure, shutter-closing means for closing the shutter to terminate anexposure, timing circuit means electrically connected with saidshutterclosing means for actuating the latter to close the shutter, saidtiming circuit means including a capacitor means which actuates saidshutter-closing means to terminate an exposure when the terminal voltageof said capacitor means rises to a given extent, said timing circuitmeans also including a photosensitive means for responding to light andelectrically connected with said capacitor means for charging the latterin response to light received by said photosensitive means, flashcircuit means for creating flash illumination to which saidphotosensitive means responds when a source of flash illumination iselectrically connected with said flash circuit means, signal-generatingcircuit means electrically connected with said flash circuit means forrendering the latter operative in synchronism with opening of theshutter and for generating an electrical signal simultaneously with thecreation of flash illumination by said flash circuit means, and chargingmeans electrically connected with said capacitor means and with saidsignal-generating circuit means for receiving the electrical signalgenerated by the latter and for charging said capacitor means to a givenextent when said signal is received by said charging means from saidsignal-generating circuit means, said charging means and capacitor meansproviding a predetermined exposure time which is diminished by theextent to which the capacitor means is charged by said photosensitivemeans in response to light received thereby during flash illumination.

2. The combination of claim 1 and wherein said photosensitive means is asolar battery.

3. The combination of claim 1 and wherein an electrical connecting meansis provided for removably connecting said flash circuit meanselectrically with said impulse-generating circuit means.

4. The combination of claim 3 and wherein said flash circuit meanscoacts with a source of flash illumination for removably receiving thelatter and said source of flash illumination rendering said flashcircuit means operative only when said source of flash illumination isconnected into said flash circuit means, so that even if the latterremains connected with said signalgenerating circuit means said flashcircuit means will not operate unless a source of flash illumination isconnected therewith.

5. The combination of claim 1 and wherein said signal-generating circuitmeans includes a coil for generating said electrical signal when saidsignal-generating circuit means renders said flash circuit meansoperative to create a flash, said charging means including an SCRelectrically connected with said coil to be rendered 7. The combinationof claim 6 and wherein said signal-generating circuit means includes abooster transformer electrically connected with said monostablemultivibrator and creating said electrical signal when saidsignal-generating circuit means renders said flash circuit meansoperative to create the flash illumination.

8. The combination of claim 1 and wherein said signal-generating circuitmeans includes only a single switch for rendering said flash circuitmeans operative in synchronism with opening of the shutter.

9. The combination of claim 1 and wherein said timing circuit meansinclues only a single switch, said switch being a normally closedtrigger switch bridging said capacitor means and adapted to be openedwhen the shutter opens to start the charging of said capacitor means.

l k l

1. In a camera, shutter-opening means for opening a shutter to start anexposure, shutter-closing means for closing the shutter to terminate anexposure, timing circuit means electrically connected with saidshutter-closing means for actuating the latter to close the shutter,said timing circuit means including a capacitor means which actuatessaid shutter-closing means to terminate an exposure when the terminalvoltage of said capacitor means rises to a given extent, said timingcircuit means also including a photosensitive means for responding tolight and electrically connected with said capacitor means for chargingthe latter in response to light received by said photosensitive means,flash circuit means for creating flash illumination to which saidphotosensitive means responds when a source of flash illumination iselectrically connected with said flash circuit means, signal-generatingcircuit means electrically connected with said flash circuit means forrendering the latter operative in synchronism with opening of theshutter and for generating an electrical signal simultaneously with thecreation of flash illumination by said flash circuit means, and chargingmeans electrically connected with said capacitor means and with saidsignal-generating circuit means for receiving the electrical signalgenerated by the latter and for charging said capacitor means to a givenextent when said signal is received by said charging means from saidsignal-generating circuit means, said charging means and capacitor meansproviding a predetermined exposure time which is diminished by theextent to which the capacitor means is charged by said photosensitivemeans in response to light received thereby during flash illumination.2. The combination of claim 1 and wherein said photosensitive means is asolar battery.
 3. The combination of claim 1 and wherein an electricalconnEcting means is provided for removably connecting said flash circuitmeans electrically with said impulse-generating circuit means.
 4. Thecombination of claim 3 and wherein said flash circuit means coacts witha source of flash illumination for removably receiving the latter andsaid source of flash illumination rendering said flash circuit meansoperative only when said source of flash illumination is connected intosaid flash circuit means, so that even if the latter remains connectedwith said signal-generating circuit means said flash circuit means willnot operate unless a source of flash illumination is connectedtherewith.
 5. The combination of claim 1 and wherein saidsignal-generating circuit means includes a coil for generating saidelectrical signal when said signal-generating circuit means renders saidflash circuit means operative to create a flash, said charging meansincluding an SCR electrically connected with said coil to be renderedconductive by the singal generated thereby, and said charging meansincluding a transistor electrically connected with said capacitor meansand with said SCR to be rendered conductive when said SCR is renderedconductive by said electrical signal for then charging said capacitormeans to said given extent.
 6. The combination of claim 1 and whereinsaid charging means includes a monostable multivibrator for receivingsaid electrical signal from said signal-generating circuit means and forthen charging said capacitor means to said given extent.
 7. Thecombination of claim 6 and wherein said signal-generating circuit meansincludes a booster transformer electrically connected with saidmonostable multivibrator and creating said electrical signal when saidsignal-generating circuit means renders said flash circuit meansoperative to create the flash illumination.
 8. The combination of claim1 and wherein said signal-generating circuit means includes only asingle switch for rendering said flash circuit means operative insynchronism with opening of the shutter.
 9. The combination of claim 1and wherein said timing circuit means inclues only a single switch, saidswitch being a normally closed trigger switch bridging said capacitormeans and adapted to be opened when the shutter opens to start thecharging of said capacitor means.